JPS606906Y2 - PCM playback device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a PCM playback device that displays tracking deviation of a video tape recorder.

The PCM audio information recorded on the video tape recorder is
After distributing and recombining (interleaving) the AD-converted information in a certain range, the signal derived as a pseudo video signal is recorded and edited at the field period, and when played back, it is converted into PCM.
A reproduction error in the reproduction signal is corrected to the extent possible, the reproduction signal is derived in accordance with the order of the beat conversion, and finally an AD conversion is performed to synthesize a distortion-free audio signal.

The main causes of errors in PCM playback signals are dropouts, where the playback signal is partially missing due to partial peeling of the magnetic surface of the video tape, and tracking deviations due to deviations in the scanning position of the rotating head. There are two points to mention.

For errors caused by dropouts, the only option is to correct errors using interleaving, and for errors caused by tracking deviations, it is enough to adjust the video tape recorder itself.

It becomes necessary to detect the frequency of errors caused only by tracking deviation among the errors that occur, and to display the tracking deviation.

Therefore, in view of the fact that playback errors based on tracking deviations have synchronicity, the present invention provides a PCM playback device that displays tracking errors when errors occur continuously in a field or an integral multiple thereof. This is what we would like to propose.

The present invention will be described below with reference to an illustrative embodiment.

The PCM playback device according to this embodiment employs the "home PCM recording and playback system signal method 2," which contains 6 data, an error correction code, and an error detection signal CRC during one horizontal synchronization period. A total of 1470 (=245×6) data are recorded in one vertical sync cycle, that is, in one recording track.

Therefore, during reproduction, errors within one horizontal synchronization period are detected using the error detection signal CRC, and data is corrected using an error correction code.

The present embodiment is configured to turn on the display lamp when an error detection output is generated based on the counting error tracking deviation, so that the error detection output of the error detection circuit 1 is turned on. A counting circuit 3 which has a counting input and the first output A of the synchronizing pulse generating circuit 2 as a reset input counts the number of error detection outputs that occur in the range of one frame at a time, and each bit of the first counting circuit 3 The logical sum output of the synchronizing pulse generating circuit 2 is applied to the D terminal of the D type flip-flop 4, and
By applying output B, the OR output at the end of one frame is inputted to the shift register 5 with the first output A as a shift pulse, and the AND output of the 8-bit output of the shift register 5 is output. is applied to the indicator lamp lighting circuit 6, and the indicator lamp 7 is lit in response to the generation of the AND output.

The synchronization pulse generation circuit 2 detects the input vertical synchronization signal of the reproduced pseudo video signal (2), divides the frequency by 172,
The falling pulse of the frequency-divided output is taken as the second output B, and the output obtained by slightly delaying the second output is derived as the first output A.

Therefore, the indicator lamp indicates that a tracking deviation has occurred when error detection outputs occur for eight consecutive frames, and therefore does not respond to dropouts that occur regardless of the field period.

Therefore, according to this embodiment, the first detection means (
a counting circuit 3, an OR circuit, and a D-type flip-flop), a second detection means (shift register 5,
Since only the tracking deviation is detected using an AND circuit), the occurrence of an error detection output due to dropout can be determined and displayed, which is very effective.

[Brief explanation of the drawing]

The figure shows a circuit block diagram of one implementation of the present invention. Explanation of main drawing numbers, 1...Error detection circuit, 3...
...Counting circuit, 4...D type flip-flop, 5...Shift register, 7...
・Indication lamp.

Claims (1)

[Scope of utility model registration request] an error detection means for detecting errors in a reproduced PCM signal derived from a video tape recorder; a first detection means for detecting the occurrence of an error detection output for each field or an integral multiple thereof; and a first detection output. a second detection means for detecting that is derived over a plurality of consecutive predetermined sections;
A PCM reproducing device in which means for driving a display means according to a second detection output are arranged respectively.